Spatial pattern of root systems of dense jujube plantation with jujube age in the semiarid loess hilly region of China

MA Li-Hui1,2, WU Pu-Te1*, and WANG You-Ke1

1Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Institute of Soil and Water Conservation, Northwest A & F University, Yangling, Shaanxi 712100, China;

2Graduate University of Chinese Academy of Sciences, Beijing 100049, China

Aims Dense jujube (Ziziphus jujuba ‘Lizao’) plantations with a spacing of 2 m between trees and 3 m between rows have been established in the semiarid hilly region of the Chinese Loess Plateau. Our objective was to study characteristics of vertical and horizontal root distribution with different tree ages.
Methods Four stands formed a chronosequence 1, 4, 8 and 11 years old. We used the trench profile method to study root distribution. We excavated four trenches 6 m long × 1 m deep × 0.8 m wide for each stand age and measured root intersects as fine (< 1 mm), medium-sized (1–3 mm) and coarse (> 3 mm) roots.
Important findings The number of root intersects increased by tree age (especially fine roots) and decreased with soil depth. 1-year-old tree root intersects were concentrated at 0–40 cm depth, and the other three older tree root intersects were mainly at 0–60 cm depth. There was no significant difference with the fine-root intersects along the horizontal distance from the trunk regardless of tree age. Different diameter root intersects showed no significant difference in the same soil layer (0–20, 20–40 and 40–60 cm) regardless of tree age and horizontal distance from trunk. The efficiency of root distribution under the densely planted pattern was determined to ensure a sustainably high fruit yield. We suggest that jujube roots formed shallow patterns vertically under the water and nutrient management measures, while it formed net patterns when densely planted. Our findings can provide a theoretical basis for efficient root management in this region.